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How it Works
Sample NIST Session
For More Information
UNIX PCs have notoriously poor internal time keeping ability. It
is not uncommon for a PC to gain or lose 1-20 seconds per DAY.
For systems where the correct time is important, an automated process
that sets the system clock to a National time standard is highly desirable.
Beagle Software's ClockWatch program provides a means for automatically
resetting the internal Linux system clock to that of the
National Institute of Standards (NIST) time by synchronizing clocks
via 2400 baud modem. The software, when installed, provides for
hourly, daily or weekly automatic resetting of the system clock.
Calls the NIST with a custom Dialers script.
When the NIST answers, the NIST measures the round-trip transmission
speed over the modem link.
The NIST sends the time in Greenwich Mean Time (GMT).
The program calculates the local time using the time zone
environmental variable and resets the UNIX system clock.
Linux Red Hat 5.x or Caldera
Modem with 2400 baud capability and Hayes Command
set directly connected to native serial port or serial ports card.
To set the system clock from the command line:
- login as: root
- type the command:
This will initiate a call to the NIST and reset the system clock.
To run administration program:
- login as: root
- type the command: cd/home/ClockWatch
- type the command: admin_menu
This will give a menu of administrative options:
- Run ClockWatch program now
- Change tty port used
- Change outside line access code
- Change automatic call schedule
- Review log
|| Runs ClockWatch program now:
This issues the command to call the NIST and
set the system clock. Call logs are printed to screen.
|| Change tty port used:
This presents the current configuration of the tty
port specified in the /usr/lib/uucp/Devices file. User can type in a new entry to replace existing entry.
|| Change outside line access code:
This presents the current entry of the dial string
specified in the /usr/lib/uucp/Systems file. User can type in a new entry to replace existing entry.
|| Change automatic call schedule:
This presents the current automatic process
commands specified in the /usr/bin/crontab file.
User can type in a new entry to replace existing entry.
This shows the call logs from the calls made to the NIST from the automatic call schedule.
Exits administration menu.
The installpkg places the program into the appropriate directory
and installs the entries in Devices, Dialers, Systems and crontab.
- login as root
- type "installpkg" from the command
- answer configuration questions for
Port to use:
This asks for which tty port to use that is
connected to a modem. The installation program
lists the tty ports currently configured in the
Examples include 'tty00', 'ttys01', ttys04'
Outside line access:
The installer should enter the access code required
(if any) for the modem chosen above to dial a long
distance number. This is often a '9'.
Whether to run automatically in crontab:
If the installer wishes to have the ClockWatch program
dial the NIST automatically, then the installer
should answer 'y' to this question. The ClockWatch
program will call the NIST out weekly at 2 AM Monday.
The time or frequency can be changed from the
Call the NIST now?:
At the end of the installation program, the installer
can choose to place a test call to the NIST to insure
that all the settings and modem are properly configured.
- login in as: root
- type from the
command line: removepkg
As an item of interest, a dump of data received from the NIST system clock
follows. This data includes the Julian date, the Greenwich Mean Time,
and the time in milliseconds that the communication takes to make the
trip from the NIST to the modem.
Sample Data from NIST:
National Institute of Standards and Technology
Telephone Time Service
MJD YR MO DA HH MM SS ST S UT1 msADV <OTM>
48662 92-02-10 01:32:32 00 0 -.2 045.0 UTC(NIST) *
48662 92-02-10 01:32:33 00 0 -.2 045.0 UTC(NIST) *
48662 92-02-10 01:32:34 00 0 -.2 045.0 UTC(NIST) *
48662 92-02-10 01:32:35 00 0 -.2 045.0 UTC(NIST) *
48662 92-02-10 01:32:36 00 0 -.2 045.0 UTC(NIST) *
48662 92-02-10 01:32:37 00 0 -.2 045.0 UTC(NIST) *
48662 92-02-10 01:32:38 00 0 -.2 045.0 UTC(NIST) *
48662 92-02-10 01:32:39 00 0 -.2 045.0 UTC(NIST) *
48662 92-02-10 01:32:40 00 0 -.2 045.0 UTC(NIST) *
48662 92-02-10 01:32:41 00 0 -.2 045.0 UTC(NIST) *
48662 92-02-10 01:32:42 00 0 -.2 045.0 UTC(NIST) *
ClockWatch The program used to call callNIST as a named
pipe and exit cu.
callNIST The program called by ClockWatch to read the
This pgm cu's to NIST, reads time and sets the
local UNIX time.
admin_menu This is a shell that gives options for changing
port, access code, crontab schedule or viewing log.
settime.sh This is a configurable shell program that sets time
on other computers on a local network.
For this program to work you need a network where
the computer installed with the ClockWatch program
is able to "rlogin" as root to the machines on the
list specified in this program.
install/ sub directory:
Install installpkg - shell for installation of ClockWatch
Remove removepkg - shell that removes ClockWatch from system.
Devices Devices Entry - tty is set at installation.
Dialers Dialers script - entry for Device, used by any 2400
Systems the number of NIST - access code is set at
crontab Line for crontab - entry to run it at 2:00 AM
logs/ sub directory:
clock_log Output of ClockWatch when run from crontab.
4th quarter '98. Beta version will be available soon.
If you are interested in evaluating the Beta version, or desire additional information,
please e-mail us or leave your request and E-mail address on the information
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